Multi-channel communication station for communicating a multi-channel PPDU and methods of reducing collisions on secondary channels in multi-channel wireless networks

ABSTRACT

Embodiments of a very-high throughput communication station and method for communicating on a primary channel and up to three or more secondary channels are generally described herein. Short-preamble detection may be performed during a contention window to detect packet transmissions on any one of the secondary channels starting within the contention window. Guard-interval detection is also performed during the contention window to detect a guard interval of a packet transmission on any one of the secondary channels. The short-preamble detection and the guard-interval detection may be performed concurrently during the contention window to determine if any of the secondary channels are busy.

This application is a continuation of U.S. patent application Ser. No.12/825,843, filed on Jun. 29, 2010, now issued as U.S. Pat. No.8,531,980, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

Embodiments pertain to wireless communications. Some embodiments relateto multi-channel wireless networks that communicate packets, such asPhysical Layer Convergence Protocol (PLCP) protocol data units (PPDUs),over multiple channels. Some embodiments relate to wireless networks anddevices that operate in accordance with one of the IEEE 802.11standards, including the IEEE 802.11n and IEEE 802.11ac standards.

BACKGROUND

One issue with communicating over wireless networks is collisionsbetween transmissions of stations of neighboring basic service sets(BSSs). Conventionally, a collision-avoidance protocol, such as acarrier-sense multiple-access with collision-avoidance (CSMA/CA)protocol, is employed to help reduce these collisions. As wirelessnetworks use additional channels employing wider bandwidths forcommunicating, the potential for collisions increases. These additionalchannels may include a primary channel and one or more secondarychannels. Collisions are particularly a concern between thetransmissions of stations of different networks that do not use the samechannel as a primary channel.

Thus, what are needed are multichannel communication stations andmethods that may help reduce the probability of collisions. What areneeded are multichannel communication stations and methods that candetect transmissions of other wireless networks on secondary channels tohelp reduce the probability of collisions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates neighboring wireless communication networks inaccordance with some embodiments;

FIG. 2 illustrates a channel and congestion aware (CCA) technique inaccordance with some embodiments;

FIG. 3 illustrates a functional block diagram of a very-high throughput(VHT) communication station in accordance with some embodiments;

FIGS. 4A and 4B illustrate collision and collision avoidance inaccordance with some embodiments; and

FIG. 5 is a procedure for communicating a multi-channel PPDU on aprimary channel and up to three or more secondary channels in accordancewith some embodiments.

DETAILED DESCRIPTION

The following description and the drawings sufficiently illustratespecific embodiments to enable those skilled in the art to practicethem. Other embodiments may incorporate structural, logical, electrical,process, and other changes. Portions and features of some embodimentsmay be included in, or substituted for, those of other embodiments.Embodiments set forth in the claims encompass all available equivalentsof those claims.

FIG. 1 illustrates neighboring wireless communication networks inaccordance with some embodiments. The neighboring wireless communicationnetworks may include two or more basic service sets (BSS), such asvery-high throughput (VHT) BSS 100 and high-throughput (HT) BSS 110. VHTBSS 100 may include VHT access point (AP) 104 and one or more VHTcommunication stations (STA) 102, and HT BSS 110 may include neighboringHT AP 114 and one or more HT communication stations (STA) 112. VHT BSS100 may be configured to operate in accordance with IEEE 802.11ac. HTBSS 110 may be configured to operate in accordance with IEEE 802.11n.

VHT BSS 100 may utilize a primary channel and up to three or moresecondary channels. HT BSS 110, on the other hand, may be limited tousing a primary channel and a single secondary channel. VHTcommunication station 102 and HT communication station 112 may utilize acontention-based collision-avoidance protocol such as the CSMA/CAprotocol to contend for access.

When the primary channel utilized by VHT BSS 100 is not the same primarychannel utilized by HT BSS 110, one or more of the secondary channels ofVHT BSS 100 may reside on the primary channel of HT BSS 110. This mayresult in a potential increase in collisions.

In accordance with some embodiments, VHT communication station 102 maybe configured to communicate a data unit, such as a PPDU, on a primarychannel and up to three or more secondary channels, and HT communicationstation 112 may be configured to communicate a PPDU on a primary channeland up to one secondary channel. VHT communication station 102 may beconfigured to reduce collisions that may occur with HT communicationstation 112 by detecting packets on the secondary channels of VHT BSS100. In these embodiments, VHT communication station 102 may performshort preamble detection and guard-interval detection during acontention window to detect a packet transmission on any one of thesecondary channels. These embodiments are described in more detailbelow.

FIG. 2 illustrates a CCA technique in accordance with some embodiments.Primary channel 208 and up to three or more secondary channels 210 maybe used by a VHT communication station, such as VHT communicationstation 102 (FIG. 1). In accordance with embodiments, VHT communicationstation 102 may perform short-preamble detection (PD) 202 during acontention window (CW) 216 to detect packet transmissions on any one ofthe secondary channels 210 from a station such as HT communicationstation 112 (FIG. 1) of the HT BSS 110 (FIG. 1) starting within thecontention window 216. VHT communication station 102 may also performguard-interval detection (GD) 204 during the contention window 216 todetect a guard-interval of a packet transmission on any one of thesecondary channels 210. The short-preamble detection 202 and theguard-interval detection 204 may be performed concurrently during thecontention window 216. The guard-interval detection 204 and theshort-preamble detection 202 are performed after a distributedcoordination function (DCF) interframe space (DIFS) 214 which isprovided, for example, after an acknowledge (ACK) packet 212. The ACKpacket 212 may have been transmitted by AP 104 of a VHT BSS 100 (FIG. 1)or by AP 114 of a HT BSS 110 acknowledging a prior receipt of a datapacket from a communication station. The ACK packet 212 may also havebeen transmitted by one of the communication stations.

The additional capability to perform short-preamble detection 202 on thesecondary channels 210 to detect signals starting in the contentionwindow 216 allows the VHT communication station 102 to detect packettransmissions on channels of a neighboring BSS, such as HT BSS 110.Unlike energy detection, which is conventionally performed to detectsignals as part of a CSMA/CA protocol, the short-preamble detection 202and the guard-interval detection 204 may detect packets that would notbe able to be detected with energy detection techniques. For example,the short-preamble detection 202 and the guard-interval detection 204may detect packets well below (e.g., up to 20 dB below) the energydetection threshold of energy detection techniques, which isconventionally about −62 dBm for secondary channels.

The packet transmissions detected on one of the secondary channels 210by either the short-preamble detection 202 or the guard-intervaldetection 204 may be signal transmissions of HT communication station112 of the neighboring HT BSS 110. The neighboring HT BSS 110 may haveits primary channel co-located on one of the secondary channels 210 ofthe VHT BSS 100.

The VHT communication station 102 may utilize the primary channel 208and up to three or more secondary channels 210 to provide transferspeeds of up to one giga-bit-per second (Gbps) and greater. The transferspeed may depend on the number of antennas used as well as the usagebandwidth. Accordingly, the transfer speed may be significantly greaterthan the transfer rate of HT communication stations, such as HTcommunication station 112. The primary channel 208 may have a bandwidthof 20 MHZ, and each secondary channel 210 may have a bandwidth of 20 MHZto provide a usage bandwidth of up to 80 MHz when three secondarychannels 210 are used, and a usage bandwidth of up to 160 MHz when up tofour additional secondary channels (not illustrated) are used. HTcommunication station 112, on the other hand, may be limited to using asingle primary channel and a single secondary channel.

The short-preamble detection 202 may include detection of apredetermined sequence comprising a short preamble indicating abeginning of a packet. The guard-interval detection 204 may include acorrelation (e.g., an autocorrelation) to detect a repeating patterncorresponding to a cyclic prefix of an OFDM symbol within one or moreframes of a packet. The detection of a cyclic prefix by theguard-interval detection 204 may indicate a valid frame within thepacket.

The short-preamble detection 202 may be performed to detect packetpreambles on any one of the secondary channels 210 starting in timeslots of the contention window 216. The short-preamble detection 202 isconfigured to be completed within a time slot of the contention window216. In these embodiments, contention window 216 may comprise aplurality of time slots. The short-preamble detection 202 may beperformed within any one or more of these time slots and may becompleted during the time slot in which it was started. Theshort-preamble detection 202 may be configured to continuously searchfor a short packet preamble during the contention window 216.

The guard-interval detection 204 may be performed during an interval ofa point-coordination function (PCF) interframe spacing (PIFS) 206immediately preceding an expiration of a backoff counter of acontention-based collision-avoidance protocol such as the CSMA/CAprotocol. When either the guard-interval detection 204 or theshort-preamble detection 202 detects a packet transmission on one of thesecondary channels 210, the secondary channel 210 is designated as abusy secondary channel. When both the guard-interval detection 204 andthe short-preamble detection 202 fail to detect a packet transmission onone of the secondary channels 210, the secondary channel 210 isdesignated as an idle secondary channel.

The VHT communication station 102 may also be configured to refrain fromtransmitting on any one of the secondary channels 210 designated as abusy secondary channel. When the primary channel 208 is idle, the VHTcommunication station 102 may also be configured to transmit a PPDU onthe primary channel 208 and any one or more of the secondary channels210 designated as an idle secondary channel. A PPDU that is transmittedon the primary channel 208 and at least one of the secondary channels210 may be referred to as a multichannel PPDU.

VHT communication station 102 may communicate on one primary channel 208and three secondary channels 210. In some other embodiments, VHTcommunication station 102 may communicate on one primary channel 208 andseven secondary channels 210.

To determine if the primary channel 208 is idle or busy, the VHTcommunication station 102 is configured to perform an energy detection,short-preamble detection 202, and guard-interval detection 204 on theprimary channel 208. The energy detection may be performed by measuringsignal levels in the primary channel 208 during the contention window216. The short-preamble detection 202 may be performed during thecontention window 216 to detect packet transmissions on the primarychannel 208. The guard-interval detection 204 may be performed duringthe contention window 216 to detect a guard-interval of a packettransmission on the primary channel 208. In this way, the VHTcommunication station 102 may determine whether the primary channel 208is idle or busy. In these embodiments, the energy detection, theshort-preamble detection 202 and the guard-interval detection 204 thatare performed on the primary channel 208 may be performed concurrentlyduring the contention window 216 along with the guard-interval detection204 and the short-preamble detection 202 that is performed on thesecondary channels 210. When the primary channel 208 is determined to beidle for a time period that includes the DIFS 214 plus the contentionwindow 216, the VHT communication station 102 may transmit a packet onthe primary channel 208 and any of the secondary channels 210 that aredesignated as idle secondary channels.

The VHT communication station 102 may also be configured to perform aCSMA/CA protocol using a DCF on the primary channel 208 for access tothe primary channel 208 and refrain from performing acollision-avoidance protocol such as the CSMA/CA protocol on thesecondary channels 210. In these embodiments, the collision-avoidanceprotocol is performed on the primary channel 208 and is not performed onthe secondary channels 210.

The VHT communication station 102 is configured to communicate with anaccess point 104 over a 20 MHz primary channel 208 and up to three ormore 20 MHz secondary channels 210 in accordance with IEEE 802.11ac. Inthese embodiments, the primary channel 208 may be used for performingthe CSMA/CA protocol as well as for communicating data packets, such asPPDUs, with the access point 104. One or more of the secondary channels210 along with the primary channel 208 may be used for communicatingmulti-channel data packets, such as multi-channel PPDUs. For example,when the channels are 20 MHz channels, a 20 MHz PPDU may be communicatedwhen the VHT communication station 102 uses only the primary channel208. A 40 MHz multi-channel PPDU may be communicated when the VHTcommunication station 102 uses the primary channel 208 and one of thesecondary channels 210. A 60 MHz multi-channel PPDU may be communicatedwhen the VHT communication station 102 uses the primary channel 208 andtwo of the secondary channels 210. An 80 MHz multi-channel PPDU may becommunicated when the VHT communication station 102 uses the primarychannel 208 and three of the secondary channels 210. Up to a 160 MHzmulti-channel PPDU may be communicated when the VHT communicationstation 102 uses the primary channel 208 and up to four additionalsecondary channels (not illustrated). For a multi-channel PPDU,different information may be transmitted on each 20 MHz channel utilizedby the multi-channel PPDU.

In some of these embodiments, the HT BSS 110 is configured tocommunicate in accordance with an IEEE 801.11n, which uses one primarychannel and one secondary channel for communicating. The packetsdetected on a secondary channel 210 by either the short-preambledetection 202 or the guard-interval detection 204 may be transmissionson a primary or secondary channel of the HT BSS 110 (FIG. 1).Accordingly, collisions with a neighboring BSS may be reduced andpossibly eliminated. It should be noted that collisions between stationsof the same BSS are generally not an issue because each BSS may use thesame primary channel for both 802.11ac stations and 802.11n stations,and stations can easily detect packet transmissions on the primarychannel of their own BSS. In the same BSS, 11n and 11ac stations use thesame primary channel, so they can detect each other's transmissionwithout a collision problem due to undetected transmissions in asecondary channel.

FIG. 3 illustrates a functional block diagram of a VHT communicationstation in accordance with some embodiments. VHT communication station300 may include, among other things, front-end circuitry 310 to receivesignals through spatially-diverse antennas 311, a short-preambledetection module 302, a guard-interval detection module 304, logical‘OR’ circuitry 306, and medium-access control (MAC) layer circuitry 308.VHT communication station 300 may be suitable for use as VHTcommunication station 102 (FIG. 1), although other configurations mayalso be suitable.

The short-preamble detection module 302 may be configured to performshort-preamble detection 202 (FIG. 2) on received data samples 301. Theguard-interval detection module 304 may be configured to performguard-interval detection 204 (FIG. 2) on received data samples 301. Thelogical ‘OR’ circuitry 306 may be configured to provide either a channelbusy or channel idle indication 307 to the MAC layer circuitry 308 todesignate the primary channel 208 (FIG. 2) and each of the secondarychannels 210 (FIG. 2) as either busy or idle. In these embodiments, thelogical ‘OR’ circuitry 306 may be configured to receive a detectionoutput from the short-preamble detection 202 and the guard-intervaldetection 204 and for the primary channel 208 and each secondary channel210 and to provide either a channel busy or channel idle indication 307to MAC layer circuitry 308. The output of the logical ‘OR’ circuitry 306may allow the MAC layer circuitry 308 to designate the primary channel208 and each secondary channel 210 as either idle or busy.

VHT communication station 300 may implement a MIMO communicationtechnique using the plurality of spatially-diverse antennas 311 tocommunicate multiple data streams concurrently over the primary channel208 and the up to three or more secondary channels 210. In theseembodiments, the VHT communication station 300 may be configured toperform the guard-interval detection 204 and the short-preambledetection 202 on the secondary channels 210 using a single one of theantennas 311, although this is not a requirement as VHT communicationstation 300 may utilize up to four or more of antennas 311 to performthe guard-interval detection 204 and the short-preamble detection 202 onthe secondary channels 210.

Although VHT communication station 300 is illustrated as having severalseparate functional elements, one or more of the functional elements maybe combined and may be implemented by combinations ofsoftware-configured elements, such as processing elements includingdigital signal processors (DSPs), and/or other hardware elements. Forexample, some elements may comprise one or more microprocessors, DSPs,application-specific integrated circuits (ASICs), radio-frequencyintegrated circuits (RFICs) and combinations of various hardware andlogic circuitry for performing at least the functions described herein.The functional elements of VHT communication station 300 may refer toone or more processes operating on one or more processing elements.

VHT communication station 300 may be a portable wireless communicationdevice, such as a personal digital assistant (PDA), a laptop or portablecomputer with wireless communication capability, a smart phone, a webtablet, a wireless telephone, a wireless headset, a pager, an instantmessaging device, a digital camera, an access point, a television, amedical device (e.g., a heart rate monitor, a blood pressure monitor,etc.), or other device that may receive and/or transmit informationwirelessly.

VHT communication station 300 operating within VHT BSS 100 may beconfigured to communicate orthogonal frequency division multiplexed(OFDM) communication signals over each of its channels including primarychannel 208 and secondary channels 210. HT BSS 110 (FIG. 1) may also beconfigured to communicate OFDM communication signals over each of itschannels. The OFDM signals may comprise symbols modulated on a pluralityof orthogonal subcarriers. Each channel may comprise a predeterminednumber of these orthogonal subcarriers. In some example embodiments,each channel may comprise fifty-two subcarriers although this is not arequirement.

Antennas 311 may comprise one or more directional or omnidirectionalantennas, including, for example, dipole antennas, monopole antennas,patch antennas, loop antennas, microstrip antennas or other types ofantennas suitable for transmission of RF signals. Instead of two or moreantennas, a single antenna with multiple apertures may be used. In theseembodiments, each aperture may be considered a separate antenna. In somemultiple-input, multiple-output (MIMO) embodiments, antennas 311 may beeffectively separated to take advantage of spatial diversity and thedifferent channel characteristics that may result between each ofantennas 311 and VHT access point 104 (FIG. 1). Antennas 311 may beseparated by up to 1/10 of a wavelength or more.

FIGS. 4A and 4B illustrate collision and collision-avoidance inaccordance with some embodiments. As illustrated in FIGS. 4A and 4B, VHTcommunication station 102 of VHT BSS 100 (FIG. 1) may communicate onprimary channel 208 and up to three secondary channels 210 illustratedas secondary channel 210A, secondary channel 210B and secondary channel210C. HT communication station 112 of HT BSS 110 (FIG. 1) maycommunicate on a primary channel 408 and secondary channel 410. In thisexample, the primary channel 408 used by that HT communication station112 coincides with secondary channel 210B used by VHT communicationstation 102. The secondary channel 410 used by HT communication station112 coincides with secondary channel 210C used by VHT communicationstation 102.

As illustrated in FIG. 4A, the VHT communication station 102 may havejust completed an 80 MHz multichannel PPDU transmission over the primarychannel 208 and all three secondary channels 210A, 210B and 210C, whichis acknowledged on each channel acknowledge packets 412. If the VHTcommunication station 102 has additional data to transmit, the VHTcommunication station 102 may start by deferring and sensing the primarychannel 208 for the time period of DIFS 214 plus the contention window216 to determine if the primary channel 208 is idle or busy.

As discussed above, the VHT communication station 102 may also sense thethree secondary channels 210A, 210B and 210C. Because HT communicationstation 112 of neighboring HT BSS 110 knows the end of the priortransmission of the VHT communication station 102, the HT communicationstation 112 may also try to access the medium by deferring for the timeperiod of DIFS 214 plus the contention window 416. In this example, thecontention window 416 of the HT communication station 112 is onetime-slot less than the contention window 216 of the VHT communicationstation 102 (e.g., due to random backoff).

If the HT communication station 112 determines that at least somechannels are idle, it may transmit a multi-channel PPDU 414 on primarychannel 408 and secondary channel 410, which correspond to the secondarychannels 210B and 210C utilized by VHT communication station 102. If theVHT communication station 102 does not perform short-preamble detection202 in the secondary channels 210 and because it may require between10˜14 micro-seconds to complete a CCA for packet transmission, the VHTcommunication station 102 would have to start guard-interval detection204 at least one slot-time before the last slot-time 218 of itscontention window 216. However, in this example, the multi-channel PPDU414 transmitted by HT communication station 112 starts from the lastslot-time 218 of the contention window 216 of VHT communication station102 and thus it does not fully overlap with the GD CCA sensing time forreliable signal detection. Thus, the VHT communication station 102 failsto detect the multi-channel PPDU 414 transmitted by HT communicationstation 112 starting from the last slot-time 218 of the contentionwindow 216. As a result, the VHT communication station 102 believes thesecondary channels 210A, 210B and 21C are idle and may transmit amulti-channel PPDU 418 over all four channels (208, 210A, 210B, 210C),which collides with the transmission of PPDU 414 of HT communicationstation 112. In this example, it is assumed that the signal level ineither secondary channel 210B or 210C is below an energy detectionthreshold level but above the short-preamble or the guard-intervaldetection levels.

As illustrated in FIG. 4B, if the VHT communication station 102 performsshort-preamble detection 202 (FIG. 2) and guard-interval detection 204(FIG. 2) during the contention window 216, the PPDU 414 of HTcommunication station 112 may be detected, causing VHT communicationstation 102 to designate secondary channels 210B and 210C as busy. As aresult, VHT communication station 102 may transmit a multi-channel PPDU419 on primary channel 208 and secondary channel 210A, avoiding acollision with PPDU 414. In this example, since short-preamble detection202 may take only about four microseconds to detect a signal in one ofthe second channels 210A, 210B or 210C, the short-preamble detection 202may be completed in the last time slot of the contention window 216 ofVHT communication station 102.

Performing short-preamble detection 202 may be used to achieve a rapidtiming sync with a transmitted frame, which may be used to help identifypositions of the guard-intervals of OFDM symbols transmitted on thesecondary channels 210. Knowledge of the guard-intervals decreases theprobability of a false detection. As a result, an increase in detectionsensitivity may be achieved when guard-interval detection followspreamble detection than can be achieved using guard-interval detectionalone. In these embodiments, the predetermined structure of a PPDU mayinclude a short-training field (STF) followed by a long-training field(LTF) followed by OFDM symbols. Each OFDM symbol may have aguard-interval. In these embodiments, when the short-preamble detectionmodule 302 identifies the start of the PPDU (e.g., by identifying theshort-training field), the guard interval detection module 304 may beconfigured to identify where the guard intervals of the PPDU are likelyto occur, thereby improving sensitivity for detecting the guardintervals that follow the long-training field. The short-preambledetection module 302 may provide an indication to the guard-intervaldetection module 304 that it has detected a short preamble, such as theshort-training field.

HT communication stations 112 of HT BSS 110 generally only performenergy detection in their secondary channel 410 to detect signaltransmissions because it is a less complex technique. As a result, HTcommunication stations 112 may fail to detect some transmissions ontheir secondary channel 410 from stations of a neighboring BSS, such asVHT BSS 100, resulting in an increase in collisions on secondary channel410. Since HT BSS 110 utilizes only a single secondary channel 410, theperformance degradation may be more tolerable than for VHT BSS 100,which uses from between three and seven secondary channels 210. Failureof the VHT communication station 102 of VHT BSS 100 to detecttransmissions on its secondary channels 210, however, may degradenetwork performance significantly. Therefore, the improved transmissiondetection technique disclosed herein may be more important for VHTcommunication station 102, particularly for VHT communication stationsconfigured to operate in accordance with IEEE 802.11ac.

FIG. 5 is a procedure for communicating a multi-channel PPDU on aprimary channel and up to three or more secondary channels in accordancewith some embodiments. Procedure 500 may be performed by a VHTcommunication station, such as VHT communication station 102 (FIG. 1).

Operation 502 comprises performing short-preamble detection during acontention window to detect packet transmissions on any one of thesecondary channels starting within the contention window.

Operation 504 comprises performing guard-interval detection during thecontention window to detect a guard interval of a packet transmission onany one of the secondary channels. The short-preamble detection and theguard-interval detection may be performed concurrently during thecontention window.

Operation 506 comprises designating a secondary channel as busy wheneither the guard-interval detection or the short-preamble detectiondetects a packet transmission on the secondary channel.

Operation 508 comprises designating a secondary channel as idle whenboth the guard-interval detection and the short-preamble detection failto detect a packet transmission on a secondary channel. In operation510, the VHT communication station may be free to transmit amultichannel PPDU on a primary channel and any one or more of thesecondary channels that are idle.

The Abstract is provided to comply with 37 C.F.R. Section 1.72(b)requiring an abstract that will allow the reader to ascertain the natureand gist of the technical disclosure. It is submitted with theunderstanding that it will not be used to limit or interpret the scopeor meaning of the claims. The following claims are hereby incorporatedinto the detailed description, with each claim standing on its own as aseparate embodiment.

What is claimed is:
 1. A communication station comprising: a transceiverconfigured to communicate on a primary 20 MHz channel and up to three ormore secondary channels including a secondary 20 MHz channel, asecondary 40 MHz channel and a secondary 80 MHz channel for operatingchannel widths of 20 MHz, 40 MHz, 80 MHz and 160 MHz; and processingcircuitry, to configure the transceiver, for Clear ChannelAssessment-Energy Detect (CCA-ED), to: issue a primary channel busycondition when a 20 MHz data unit is detected in the primary 20 MHzchannel at or above a first predetermined energy level; issue asecondary channel busy condition when a primary channel busy conditionhas not been issued and when any signal is detected within the secondary20 MHz channel at or above a second predetermined energy level; andissue a secondary channel busy condition when a primary channel busycondition has not been issued and when a 20 MHz data unit is detected inthe secondary 20 MHz channel or a 20 MHz sub-channel of either thesecondary 40 MHz channel or the secondary 80 MHz channel at or above athird predetermined energy level, wherein a 20 MHz data unit in theprimary 20 MHz channel an energy level at or above the firstpredetermined energy level and below the third predetermined energylevel is detected using preamble detection followed by a guard intervaldetection, the preamble detection detecting a start of a Physical LayerConvergence Protocol (PLCP) protocol data units (PPDU).
 2. Thecommunication station of claim 1 wherein the 20 MHz data unit is a 20MHz Physical Layer Convergence Protocol (PLCP) protocol data unit(PPDU).
 3. The communication station of claim 2 wherein the secondpredetermined energy level is greater than the third predeterminedenergy level, and wherein the third predetermined energy level isgreater than the first predetermined energy level.
 4. The communicationstation of claim 3 station is further configured to: perform an EDtechnique to detect a 20 MHz PPDU in the primary 20 MHz channel at orabove the first predetermined energy level; and perform an ED techniqueto detect a 20 MHz PPDU in the secondary 20 MHz channel or a 20 MHzsub-channel of either the secondary 40 MHz channel or the secondary 80MHz channel at or above the third predetermined energy level.
 5. Acommunication station comprising: a transceiver configured tocommunicate on a primary 20 MHz channel and up to three or moresecondary channels including a secondary 20 MHz channel, a secondary 40MHz channel and a secondary 80 MHz channel for operating channel widthsof 20 MHz, 40 MHz, 80 MHz and 160 MHz and to perform channel assessmentin accordance with an energy detection (ED) technique; and processingcircuitry, wherein as part of the ED technique, the processing circuitryis to configure the transceiver to: issue a primary channel busycondition when a 20 MHz data unit is detected in the primary 20 MHzchannel at or above a first predetermined energy level; and issue asecondary channel busy condition when a primary channel busy conditionhas not been issued and when: any signal is detected within thesecondary 20 MHz channel at or above a second predetermined energylevel; or a 20 MHz data unit is detected in the secondary 20 MHz channelor a 20 MHz sub-channel of either the secondary 40 MHz channel or thesecondary 80 MHz channel at or above a third predetermined energy level,wherein the 20 MHz data unit is a 20 MHz Physical Layer ConvergenceProtocol (PLCP) protocol data unit (PPDU), wherein the secondpredetermined energy level is greater than the third predeterminedenergy level, and wherein the third predetermined energy level isgreater than the first predetermined energy level, and wherein thestation is further configured to: perform preamble detection to detect a20 MHz PPDU in the primary 20 MHz channel at or above the firstpredetermined energy level; and perform guard interval detection todetect a 20 MHz PPDU in the secondary 20 MHz channel or a 20 MHzsub-channel of either the secondary 40 MHz channel or the secondary 80MHz channel at or above the third predetermined energy level.
 6. Amethod performed by a communication station comprising: configuring atransceiver to communicate on a primary 20 MHz channel and up to threeor more secondary channels including a secondary 20 MHz channel, asecondary 40 MHz channel and a secondary 80 MHz channel for operatingchannel widths of 20 MHz, 40 MHz, 80 MHz and 160 MHz; and performingchannel assessment for Clear Channel Assessment-Energy Detect (CCA-ED),wherein as part of the CCA-ED, the method includes: issuing a primarychannel busy condition when a 20 MHz data unit is detected in theprimary 20 MHz channel at or above a first predetermined energy level;issuing a secondary channel busy condition when a primary channel busycondition has not been issued and when any signal is detected within thesecondary 20 MHz channel at or above a second predetermined energylevel; and issue a secondary channel busy condition when a primarychannel busy condition has not been issued and when a 20 MHz data unitis detected in the secondary 20 MHz channel or a 20 MHz sub-channel ofeither the secondary 40 MHz channel or the secondary 80 MHz channel ator above a third predetermined energy level, wherein a 20 MHz data unitin the primary 20 MHz channel having an energy level at or above thefirst predetermined energy level and below the third predeterminedenergy level is detected using preamble detection followed by a guardinterval detection, the preamble detection detecting a start of aPhysical Layer Convergence Protocol (PLCP) protocol data units (PPDU).7. The method of claim 6 wherein the 20 MHz data unit is a 20 MHzPhysical Layer Convergence Protocol (PLCP) protocol data unit (PPDU). 8.The method of claim 7 wherein the second predetermined energy level isgreater than the third predetermined energy level, and wherein the thirdpredetermined energy level is greater than the first predeterminedenergy level.
 9. The method of claim 7 further comprising: performing anED technique to detect a 20 MHz PPDU in the primary 20 MHz channel at orabove the first predetermined energy level; and performing an EDtechnique to detect a 20 MHz PPDU in the secondary 20 MHz channel or a20 MHz sub-channel of either the secondary 40 MHz channel or thesecondary 80 MHz channel at or above the third predetermined energylevel.
 10. A method performed by a communication station comprising:configuring a transceiver to communicate on a primary 20 MHz channel andup to three or more secondary channels including a secondary 20 MHzchannel, a secondary 40 MHz channel and a secondary 80 MHz channel foroperating channel widths of 20 MHz, 40 MHz, 80 MHz and 160 MHz; andperforming channel assessment in accordance with an energy detection(ED) technique, wherein as part of the ED technique, the methodincludes: issuing a primary channel busy condition when a 20 MHz dataunit is detected in the primary 20 MHz channel at or above a firstpredetermined energy level; and issuing a secondary channel busycondition when a primary channel busy condition has not been issued andwhen: any signal is detected within the secondary 20 MHz channel orabove a second predetermined energy level; or a 20 MHz data unit isdetected in the secondary 20 MHz channel or a 20 MHz sub-channel ofeither the secondary 40 MHz channel or the secondary 80 MHz channel ator above a third predetermined energy level, wherein the 20 MHz dataunit is a 20 MHz Physical Layer Convergence Protocol (PLCP) protocoldata unit (PPDU), wherein the second predetermined energy level isgreater than the third predetermined energy level, and wherein the thirdpredetermined energy level is greater than the first predeterminedenergy level, and wherein the method further comprises: performingpreamble detection to detect a 20 MHz PPDU in the primary 20 MHz channelat or above the first predetermined energy level; and performing guardinterval detection to detect a 20 MHz PPDU in the secondary 20 MHzchannel or a 20 MHz sub-channel of either the secondary 40 MHz channelor the secondary 80 MHz channel at or above the third predeterminedenergy level.
 11. A non-transitory computer-readable storage medium thatstores instructions for execution by one or more processors of a devicethat is configurable to communicate on a primary 20 MHz channel and upto three or more secondary channels including a secondary 20 MHzchannel, a secondary 40 MHz channel and a secondary 80 MHz channel foroperating channel widths of 20 MHz, 40 MHz, 80 MHz and 160 MHz; whereinthe instructions configure the device to perform channel assessment forCCA-Energy Detect (Clear Channel Assessment-ED), wherein as part of theCCA-ED, the one or more processors are configured to: issue a primarychannel busy condition when a 20 MHz data unit is detected in theprimary 20 MHz channel at or above a first predetermined energy level;issue a secondary channel busy condition when a primary channel busycondition has not been issued and when any signal is detected within thesecondary 20 MHz channel at or above a second predetermined energylevel; and issue a secondary channel busy condition when a primarychannel busy condition has not been issued and when a 20 MHz data unitis detected in the secondary 20 MHz channel or a 20 MHz sub-channel ofeither the secondary 40 MHz channel or the secondary 80 MHz channel ator above a third predetermined energy level, wherein a 20 MHz data unitin the primary 20 MHz channel having an energy level at or above thefirst predetermined energy level and below the third predeterminedenergy level is detected using preamble detection followed by a guardinterval detection, the preamble detection detecting a start of aPhysical Layer Convergence Protocol (PLCP) protocol data units (PPDU).12. The non-transitory computer-readable storage medium of claim 11wherein the 20 MHz data unit is a 20 MHz Physical Layer ConvergenceProtocol (PLCP) protocol data unit (PPDU).
 13. The non-transitorycomputer-readable storage medium of claim 12 wherein the secondpredetermined energy level is greater than the third predeterminedenergy level, and wherein the third predetermined energy level isgreater than the first predetermined energy level.
 14. Thenon-transitory computer-readable non-transitory computer-readablestorage medium of claim 13 wherein the one or more processors arefurther configured to: perform an ED technique to detect a 20 MHz PPDUin the primary 20 MHz channel at or above the first predetermined energylevel; and perform an ED technique to detect a 20 MHz PPDLI in thesecondary 20 MHz channel or a 20 MHz sub-channel of either the secondary40 MHz channel or the secondary 80 MHz channel at or above the thirdpredetermined energy level.
 15. A non-transitory computer-readablestorage medium that stores instructions for execution by one or moreprocessors of a device that is configurable to communicate on a primary20 MHz channel and up to three or more secondary channels including asecondary 20 MHz channel, a secondary 40 MHz channel and a secondary 80MHz channel for operating channel widths of 20 MHz, 40 MHz, 80 MHz and160 MHz; wherein the instructions configure the device to performchannel assessment in accordance with an energy detection (ED)technique, wherein as part of the ED technique, the one or moreprocessors are configured to: issue a primary channel busy conditionwhen a 20 MHz data unit is detected in the primary 20 MHz channel at orabove a first predetermined energy level; and issue a secondary channelbusy condition when a primary channel busy condition has not been issuedand when: any signal is detected within the secondary 20 MHz channel ator above a second predetermined energy level; or a 20 MHz data unit isdetected in the secondary 20 MHz channel or a 20 MHz sub-channel ofeither the secondary 40 MHz channel or the secondary 80 MHz channel ator above a third predetermined energy level, wherein the 20 MHz dataunit is a 20 MHz Physical Layer Convergence Protocol (PL CP) protocoldata unit (PPDU), wherein the second predetermined energy level isgreater than the third predetermined energy level, wherein the thirdpredetermined energy level is greater than the first predeterminedenergy level, and wherein the one or more processors are furtherconfigured to: perform preamble detection to detect a 20 MHz PPDU in theprimary 20 MHz channel at or above the first predetermined energy level;and perform guard interval detection to detect a 20 MHz PPDU in thesecondary 20 MHz channel or a 20 MHz sub-channel of either the secondary40 MHz channel or the secondary 80 MHz channel at or above the thirdpredetermined energy level.